Air vs Ground source heat pums

[Theo]

For comparison I used to use about 12420kWh of oil a year. Now, with a 13kW ASHP, electricity consumption for heating and hot water over the first year was 2867.5kWh.

So if your usage is about 8000kWh you may be ok with a 10kW ASHP, although the calcs will tell you about your peak instantaneous losses on freezing days, which is what matters for sizing. For my draughty averagely-insulated house the 13kW is plenty (I actually bumped up from 10kW to get a slightly quieter unit, not because the extra heat was needed) and has worked fine down to -9C, which is the coldest we've had.

Unless you live in Greenland, I expect you'll find it's well within the capability of an ASHP, even on the coldest winter days.

Theo

[ajh]

Thanks for the info, did you fit it yourself or us an MCS accredited installer, necessary for the filling with refrigerant I think?

So yours is an air to water system?

Until I get too decrepit I can save myself the 700 odd quid a year it would cost to run with electricity but I have already mooted the idea for my Daughter's house.

[Theo]

It's a monobloc air2water, so the refrigerant is entirely sealed inside from the factory. Just electricity and water go in and hot water comes out. I considered DIY but it would have been too big a job for me to do single handed (heavy stuff moving, pipework, uninstalling the oil boiler etc), so went with an installer. A lot of it is easier with several people on the job at once to feed through pipes, cables etc.

If you have a source of your own wood there's something to be said for that, OTOH it's nice to have a warm house all day without lifting a finger.

Theo

[ajh]

I seem to be able to source some even after being out of the trade for several years, I have none of my own and there is some work and small expense incurred.

The heat is less controllable than central heating but not a problem for me.

In my case there is also the benefit that sat around doing nothing I would put on weight and cutting logs is a fairly gentle exercise which only sends my heart rate up to a safe level where running or cycling pushes it above my safe limit of 150bpm.

It is not an option for the vast majority of housing.

[Vir Campestris]

Hmm. I had a nasty surprise on my first house. It had gas fired central heating, and we had a cold snap.

It turned out they'd done their calculations, and it could cope down to an outside temperature around freezing, which is probably OK most of the time in southern England.

It got to -10C. And once the outside temperature had got below freezing the internal temperature started to follow it down. We had the boiler running 24/7, and were using resistive electric as well.

You need to size your heat pump for the worst possible weather, not the average. And remember that that worst possible weather is likely to be when it is least efficient.

Andy